1. Field of the Invention
The present invention relates to a charged beam gun where a high positive voltage is applied in order to accelerate charged particles, such as a field emission type electron gun of a scanning electron microscope system.
2. Description of the Related Art
For a charged beam gun for an apparatus of which a high ultimate vacuum and a good-quality vacuum are required, such as an electron beam apparatus and an ion beam apparatus, vacuum degassing (or baking) of the charged beam gun is performed in order to achieve a high-level and good-quality vacuum in the body thereof. Here, having regard to thermal resistance of the charged beam gun, maintenance of the charged beam gun, and so on, a high-voltage cable unit and a vacuum container that is the body of the charged beam gun are configured as separate structures. Accordingly the charged beam gun has a structure configured by assembling the above-mentioned two portions and connecting a high-voltage power supply unit to the assembly. Dielectric strength of a section that provides an electrical connection between a power supply part and a body part is important for such a charged beam gun.
The related art for increasing the dielectric strength is, for example, to employ a method in which space for the electrical connection between the power supply part and the body part is provided to increase a creepage distance. Moreover, as another prior art, it is suggested to fill an insulating liquid having fluorine as a main ingredient into the space for the electrical connection between the power supply part and the body part, as disclosed in Japanese Patent Application Laid-open Publication